The present invention relates to methods for planarization of metal-containing (preferably, Group VIII, and more preferably, platinum-containing) surfaces, particularly in the fabrication of semiconductor devices.
Films of metals and metal oxides, particularly the heavier elements of Group VIII, are becoming important for a variety of electronic and electrochemical applications. This is at least because many of the Group VIII metal films are generally unreactive, resistant to oxidation or retard the diffusion of oxygen, and are good conductors. Oxides of certain of these metals also possess these properties, although perhaps to a different extent.
Thus, films of Group VIII metals, their alloys, and metal oxides, particularly the second and third row metals (e.g., Ru, Os, Rh, Ir, Pd, and Pt) have suitable properties for a variety of uses in integrated circuits. For example, they can be used in integrated circuits for barrier materials, for example. They are particularly suitable for use as barrier layers between the dielectric material and the silicon substrate in memory devices. Furthermore, they are suitable as the plate (i.e., electrode) itself in capacitors.
Platinum is one of the candidates for use as an electrode for high dielectric capacitors. Capacitors are the basic charge storage devices in random access memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and now ferroelectric memory (FE RAM) devices. They consist of two conductors, such as parallel metal or polysilicon plates, which act as the electrodes (i.e., the storage node electrode and the cell plate capacitor electrode), insulated from each other by a dielectric material (a ferroelectric dielectric material for FE RAMs). Thus, there is a continuing need for methods and materials for the processing of Group VIII metal-containing films, preferably, platinum-containing films.
Many surfaces that result during the formation of Group VIII metal-containing films, particularly in the wafer fabrication of semiconductor devices, do not have uniform height, and therefore, the wafer thickness is also non-uniform. Further, surfaces may have defects such as crystal lattice damage, scratches, roughness, or embedded particles of dirt or dust. For various fabrication processes to be performed, such as lithography and etching, height non-uniformities and defects at the surface of the wafer must be reduced or eliminated. Also, excess material may need to be removed to form a structure with selectivity relative to the underlying substrate. Planar removal of a substrate""s top surface is also used to isolate certain features electrically. Various planarization techniques are available to provide such reduction and/or elimination. One such planarization technique includes mechanical and/or chemical-mechanical polishing (abbreviated herein as xe2x80x9cCMPxe2x80x9d).
The process of planarization is used to remove material, and preferably achieve a planar surface, over the entire chip and wafer, sometimes referred to as xe2x80x9cglobal planarity.xe2x80x9d Conventionally, the process of planarization, and particularly CMP, involves the use of a wafer holder that holds a wafer, a polishing pad, and an abrasive slurry that includes a dispersion of a plurality of abrasive particles in a liquid. The abrasive slurry is applied so that it contacts the interface of the wafer and the polishing pad. A table or platen has a polishing pad thereon. The polishing pad is applied to the wafer at a certain pressure to perform the planarization. At least one of the wafer and a polishing pad are set in motion relative to the other. In some planarization processes, the wafer holder may or may not rotate, the table or platen may or may not rotate and/or the platen may be moved in a linear motion as opposed to rotating. There are numerous types of planarization units available which perform the process in different manners. Alternatively, the polishing pad and abrasive slurry may be replaced by a fixed abrasive article that includes a plurality of abrasive particles dispersed within a binder adhered to at least one surface of a backing material.
The planarization of a surface that includes platinum and other Group VIII metals typically involves mechanical polishing, as opposed to chemical-mechanical polishing, because they are relatively chemically inert and/or have relatively few volatile products. Such mechanical polishing uses alumina, silica, or other abrasive particles to remove the metal physically. Unfortunately, mechanical polishing tends to smear (e.g., deform) the metals, leaving metal over undesired portions of the wafer surface, and leaving scratches in either the metal itself or other areas on the wafer surface. Also, many commercially available abrasive slurries do not effectively planarize platinum or other Group VIII metal-containing surfaces either because no material is removed or the resultant surface has defects therein.
Thus, there is still a need for methods for planarizing an exposed surface of a substrate that includes platinum and/or other Group VIII metals, particularly in the fabrication of semiconductor devices.
The present invention provides methods that overcome many of the problems associated with the planarization of a surface, particularly one that includes platinum, another of the Group VIIIB metals, and/or a Group IB metal. Preferably, the methods of the present invention are effective for the planarization of a surface containing at least one of the second and third row metals of Group VIIIB (i.e., Groups 8, 9, and 10, which includes Rh, Ru, Ir, Pd, Os, and Pt) and Group IB (i.e., Au and Ag). More preferably, the methods of the present invention are effective for the planarization of a surface containing at least one of Rh, Ru, Ir, Pd, and Pt. Such a surface is referred to herein as a xe2x80x9cmetal-containing surface.xe2x80x9d That is, a xe2x80x9cmetal-containing surfacexe2x80x9d refers to an exposed region having a metal present, preferably at least one metal of Group VIIIB and Group IB present. In such an exposed region, the metal is preferably present in an amount of at least about 10 atomic percent, more preferably at least about 20 atomic percent, and most preferably at least about 50 atomic percent, of the composition of the region, which may be provided as a layer, film, coating, etc., to be planarized (e.g., via chemical-mechanical or mechanical planarization or polishing) in accordance with the present invention. The surface preferably includes one or more Group VIIIB and/or Group IB metals in elemental form or an alloy thereof (with each other and/or one or more other metals of the Periodic Table), as well as oxides, nitrides, and suicides thereof. More preferably, the surface includes (and most preferably, consists essentially of) one or more Group VIIIB and/or Group IB metals in elemental form or an alloy of such metals only.
The methods of the present invention involve planarizing a surface using a planarization composition that preferably includes a halogen-containing compound and a halide salt therein (dissolved or dispersed therein). A preferred group of halogen-containing compounds include the halogens (e.g., F2, Cl2, Br2, and I2), the interhalogens (e.g., ClBr, IBr, ICl, BrF, ClF, ClF3, BrF3, ClF5, IF5, and IF7), and halogen-generating compounds (e.g., XeF2, HgF2, SF4, alkyl halides, and complexes of X2 with organic bases). The halide salts can be inorganic salts (e.g., NaI, KCl, KBr, and NH4F) or organic salts (e.g., Et4NBr, Me3NHCl, and Me4NF).
Herein, as is conventionally understood, xe2x80x9cplanarizingxe2x80x9d or xe2x80x9cplanarizationxe2x80x9d refers to the removal of material from a surface, whether it be a large or small amount of material, either mechanically, chemically, or both. This also includes removing material by polishing. As used herein, xe2x80x9cchemical-mechanical polishingxe2x80x9d and xe2x80x9cCMPxe2x80x9d refer to a dual mechanism having both a chemical component and a mechanical component, wherein corrosion chemistry and fracture mechanics both play a roll in the removal of material, as in wafer polishing.
Preferably, the halogen-containing compound is present in the composition in an amount of at least about 0.1% by weight, and more preferably, in an amount of no greater than about 50% by weight. Most preferably, the halogen-containing compound is present in the composition in an amount of about 1% to about 10% by weight.
Preferably, the halide salt is present in the composition in an amount of at least about 0.1% by weight, and more preferably, in an amount of no greater than about 50% by weight. Most preferably, the halide salt is present in the composition in an amount of about 1% to about 10% by weight.
The planarization composition can optionally include abrasive particles, thereby resulting in an abrasive slurry, and be used in planarization techniques with conventional polishing pas that do not have abrasive particles embedded therein. Alternatively, the planarization composition without abrasive particles therein can be used with fixed abrasive articles (also referred to as abrasive polishing pads) in place of conventional polishing pads. Such fixed abrasive articles include a plurality of abrasive particles dispersed within a binder adhered to at least one surface of a backing material. If the halogen-containing compound and/or halide salt are not stable in a composition with abrasive particles (i.e., an abrasive slurry), they may be provided by separate delivery systems and/or in separate compositions and mixed at the point of use. Alternatively, the composition may be stabilized by the addition of surfactants, chelating agents, phase transfer catalysts, emulsifiers, or other solvents.
In one aspect of the present invention, a planarization method is provided that includes: positioning a metal-containing surface of a substrate (preferably, a semiconductor substrate or substrate assembly such as a silicon wafer) to interface with a polishing surface; supplying a planarization composition in proximity to the interface; and planarizing the metal-containing surface. The metal-containing surface includes a metal selected from the group consisting of a Group VIIIB metal, a Group IB metal, and a combination thereof. The planarization composition includes a halogen-containing compound and a halide salt. Herein, xe2x80x9caxe2x80x9d or xe2x80x9canxe2x80x9d or xe2x80x9cthexe2x80x9d mean xe2x80x9cone or morexe2x80x9d or xe2x80x9cat least one.xe2x80x9d Thus, various combinations of halogen-containing compounds and halide salts can be used in the planarization compositions described herein.
In another aspect of the invention, there is provided a planarization method that includes: providing a semiconductor substrate or substrate assembly including at least one region of a platinum-containing surface; providing a polishing surface; providing a planarization composition at an interface between the at least one region of platinum-containing surface and the polishing surface; and planarizing the at least one region of platinum-containing surface; wherein the planarization composition includes a halogen-containing compound and a halide salt.
In yet another aspect of the invention, there is provided a planarization method that includes: positioning a metal-containing surface of a substrate to interface with a polishing surface, wherein the metal-containing surface includes a metal selected from the group consisting of a Group VIIIB metal, a Group IB metal, and a combination thereof; supplying a planarization composition in proximity to the interface; and planarizing the substrate surface. In this embodiment, the planarization composition includes: a halogen-containing compound selected from the group consisting of F2, Cl2, Br2, I2, ClBr, IBr, ICl, BrF, ClF, ClF3, BrF3, ClF5, IF5, IF7, XeF2, HgF2, SF4, alkyl halides, and complexes of X2 with organic bases, and combinations thereof; and a halide salt selected from the group consisting of NaI, KCl, KBr, NH4F, Et4NBr, Me3NHCl, Me4NF, and combinations thereof.
In still another aspect of the invention, there is provided a planarization method that includes: providing a semiconductor substrate or substrate assembly including at least one region of a platinum-containing surface; providing a polishing surface; providing a planarization composition at an interface between the at least one region of platinum-containing surface and the polishing surface; and planarizing the at least one region of platinum-containing surface. In this embodiment, the planarization composition includes: a halogen-containing compound selected from the group consisting of F2, Cl2, Br2, I2, ClBr, IBr, ICl, BrF, ClF, ClF3, BrF3, ClF5, IF5, IF7, XeF2, HgF2, SF4, alkyl halides, and complexes of X2 with organic bases, and combinations thereof; and a halide salt selected from the group consisting of NaI, KCl, KBr, NH4F, Et4NBr, Me3NHCl, Me4NF, and combinations thereof.
The present invention also provides a planarization method for use in forming an interconnect that includes: providing a semiconductor substrate or substrate assembly having a patterned dielectric layer formed thereon and a metal-containing layer formed over the patterned dielectric layer, wherein the metal-containing layer includes a metal selected from the group consisting of a Group VIIIB metal, a Group IB metal, and a combination thereof; positioning a first portion of a polishing surface for contact with the metal-containing layer; providing a planarization composition in proximity to the contact between the polishing surface and the metal-containing layer; and planarizing the metal-containing layer; wherein the planarization composition includes a halogen-containing compound and a halide salt.
The present invention further provides a planarization method for use in forming an interconnect that includes: providing a semiconductor substrate or substrate assembly having a patterned dielectric layer formed thereon and a metal-containing layer formed over the patterned dielectric layer, wherein the metal-containing layer includes a metal selected from the group consisting of a Group VIIIB metal, a Group IB metal, and a combination thereof; positioning a first portion of a polishing surface for contact with the metal-containing layer; providing a planarization composition in proximity to the contact between the polishing surface and the metal-containing layer; and planarizing the metal-containing layer. In this embodiment, the planarization composition includes: a halogen-containing compound selected from the group consisting of F2, Cl2, Br2, I2, ClBr, IBr, ICl, BrF, ClF, ClF3, BrF3, ClF5, IF5, IF7, XeF2, HgF2, SF4, alkyl halides, and complexes of X2 with organic bases, and combinations thereof; and a halide salt selected from the group consisting of NaI, KCl, KBr, NH4F, Et4NBr, Me3NHCl, Me4NF, and combinations thereof.
As used herein, xe2x80x9csemiconductor substrate or substrate assemblyxe2x80x9d refers to a semiconductor substrate such as a base semiconductor layer or a semiconductor substrate having one or more layers, structures, or regions formed thereon. A base semiconductor layer is typically the lowest layer of silicon material on a wafer or a silicon layer deposited on another material, such as silicon on sapphire. When reference is made to a substrate assembly, various process steps may have been previously used to form or define regions, junctions, various structures or features, and openings such as capacitor plates or barriers for capacitors.